Why do men sometimes have trouble achieving orgasm? Is the problem physical or emotional? Sexploration answers your queries. Have an intimate question? E-mail the author. He'll tackle select questions in future columns.

Q: I am a 49-year-old male and at times I have trouble ejaculating. I seem to build up to the point of ejaculation, but then it subsides and yet I remain erect. Why is this?

A: When you were 20, I bet you wished you could hold back that leap over the falls, no?

What you have, my fallow friend, is called delayed ejaculation or anorgasmia (which literally means no orgasm at all, but the two are sometimes used interchangeably).

Read through the rest of this week’s questions and answers for more information on why you might be experiencing this, but one reason could be your age. Sorry. The older we guys get, the longer it takes us.

You could argue — and I say why not? — that this makes you a much better lover than your average 25-year-old slam-bam “Whoops! Uh, sorry” guy. Women needn’t worry about your staying power.

But if it troubles you, and I guess it does or you wouldn’t be asking, see a urologist who specializes in male sexual dysfunction to work through the possibilities you’ll find below.

Q: I’m a single male who can maintain an erection but can't ejaculate when having sex, although I am able to when I masturbate. Three years ago I had surgery on a disk in my lower back, and have been taking Paxil for a year. Could this be the cause of my inability to climax? My doctor says no on nerve damage, otherwise I would not be able to get an erection. What should I do?

A: You, too, should see a urologist (no I don’t get a kickback). Do not completely discount the back surgery as a factor just yet; the nerve pathways for erection and ejaculation are not completely identical.

But the much more likely culprit is the Paxil. Since the 1980s, doctors have known that anorgasmia can be a side effect of certain antidepressants. Sometimes they even prescribe them for guys who false-start. Seems the drugs gum up the serotonin cycle in the brain, which also happens to play a big role in climax. Antihypertensive and antipsychotic drugs, and alcohol, can also flash the red stop light.

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Q: I have been in several relationships since my divorce more than seven years ago. When the relationships have turned sexual, I have no problems with erections. However, I have great difficulty reaching ejaculation. This has caused some problems in the relationships, because the partners have taken this personally. What can I do to find the source of this problem? It seems to have started after a very ugly and nasty divorce. Is this a physical problem or an emotional one?

A: Could be either. “Pre-existent psychological traumas,” like, say, a nasty divorce, can create anorgasmia, according to guidelines on male infertility that were issued last year by the European Association of Urology. So could your education (spend any time in all-boys religious boarding schools?). Or your parents’ attitudes about sex. Or any of a dozen other psychological barriers like performance anxiety with a new lover.

It could also be any of the organic causes cited above, or even some sort of bacterial prostate infection.

Therapies for anorgasmia range from psychological counseling, to sex therapy, to drugs, to the use of vibrators on the penis (it’s not just for the women, you know!) and electro ejaculation, a last-ditch effort sometimes used during in vitro fertilization that involves anesthesia and an electrical rod up your rectum to force release of ejaculate.

Q: I have been with my wife since junior high school. When we are together I can maintain an erection for hours with no problem. One time we had an all night session and I orgasmed five times. Is this normal?

A: Show off.

Brian Alexander is a California-based writer who covers sex, relationships and health. He is a contributing editor at Glamour and the author of "Rapture: How Biotech Became the New Religion" (Basic Books).